It has long been recognized that in any jaw chuck arrangement operating at other than relatively low rotative speeds, the centrifugal force developed on the chuck jaws as rotative speeds increase may cause an appreciable change in the force by which the jaws engage the workpiece. Accordingly, where the jaws are arranged for inside gripping, an increase in rotative speed will increase the centrifugal force applied by the jaws to the workpiece and may effect a substantial distortion of the workpiece. This, particularly with relatively thin workpieces, often requires that the operating speed of the chuck be kept much below the speed at which cutting could otherwise be carried out with a resulting increase in the time required for a given operation and consequent greater expense. Conversely, where the chuck is arranged for outside gripping, centrifugal force will tend to diminish the force by which the chuck grips the workpiece, even to such a point that if the workpiece is subjected to substantial cutting pressure, it may slip in the chuck. This, again, often requires the operating speed of the chuck to be held below what would otherwise be possible.
This problem has long been known and several types of counterbalance chucks have in the past been offered. These, however, have usually been either relatively complex, requiring parts having close dimensional tolerances, and requiring precisely constructed means for evenly applying a counterbalancing force onto each jaw. These chucks have been truly effective for only a narrow range of speeds and tend at other speeds to distort the workpiece to an undesirable extent. They also have other disadvantages well known to the trade.
Accordingly, the objects of the invention include:
1. To provide a counterbalanced chuck as above set forth wherein the counterbalancing means is effective in a substantially constant manner at all normal operating speeds of a given chuck, whereby the force by which the chuck engages the workpiece will remain substantially constant throughout the entire range of normal operating speeds for such given chuck.
2. To provide a device, as aforesaid, which will constitute only a simple alteration in a wide range of otherwise standard chucks.
3. To provide apparatus, as aforesaid, which is simple and may be added to a wide range of otherwise standard chuck designs with only simple and inexpensive modifications thereof.
4. To provide apparatus, as aforesaid, wherein the changes required from otherwise standard chuck designs may be applied without adversely affecting the operation of the chuck.
Other objects and purposes of the invention will become apparent to persons acquainted with apparatus of this general type upon reading the following specification and inspection of the accompanying drawings.